How and Where to Inject Insulin

If you have type 1 diabetes (T1D) or care for someone who does, you know that insulin is a life-sustaining medication. Understanding where and how to inject insulin is an important long-term lesson for anyone living with or caring for someone with T1D. Here are the basics to know.

What Are the Different Options for Taking Insulin?

There are three main ways of taking insulin:

• Traditional vial and syringe

• Insulin pen and pen needle. The pen is pre-filled with the medication, and a pen needle screws on to the top to give the shot.

• Insulin pump, which delivers rapid-acting insulin continuously through an infusion set attached to the body.

In addition to different insulin delivery methods, there are different types of insulin, including:

• Long-acting insulin, also called basal insulin.

• Rapid-acting insulin for mealtimes, also called bolus insulin.

The traditional way to take insulin is by through multiple daily injections (MDI), with one injection of basal insulin daily and then rapid-acting insulin for mealtimes. This can require a person to take subcutaneous (under the skin) injections at least four times daily in order to keep their blood sugar managed.

Many people still take insulin this way, but it’s no longer the only option: Technology has evolved over the last several decades as a means of decreasing the burden of diabetes for those living with it or caring for a person who has it. The T1D community can now utilize smart insulin pens that have connected apps on smart phones. This allows providers to program insulin doses into the phone app so the individual does not have to do complex math calculations for mealtime insulin doses. Additionally, insulin pumps offer an option to deliver rapid-acting insulin continuously through an infusion set attached to the body. At mealtimes you enter your blood sugar and what you’re eating into the pump, and it delivers a corresponding bolus (rapid-acting) insulin dose.

Insulin pumps can also communicate with devices called continuous glucose monitors (CGMs) in order to continuously monitor blood sugar levels and deliver adjusted insulin doses in real time. Known as hybrid-closed loop systems, these systems have been shown to provide profound blood sugar control and improve the quality of life for individuals with T1D and their caregivers.

Common Injection Sites for Insulin

There are various sites on the body that can be used for insulin injection, and the rate of absorption depends on the insulin injection site. In order of fastest to slowest absorption, the options are:

• Abdomen

• Back of upper arm

• Lower back

• Upper outer thigh

Rotating injection sites is key to avoid getting knots underneath the skin, which are called “areas of lipohypertrophy.” It is also very important to rotate sites with each injection and avoid injecting into areas of scar tissue.

For example, if you are injecting insulin into the abdomen (often the most common site for injection), it helps to rotate injection sites around your belly button like a clock, making sure to be at least 2 inches from the belly button itself.

Tips for Injecting Insulin

You should generally inject insulin into the skin at a 90 degree angle. In the case of longer pen needles or syringes (6.8-12.7mm), you will probably be advised to “pinch an inch” of skin when injecting. The goal is to get the insulin into the subcutaneous area under the skin and avoid the muscle. If insulin is injected into the muscle it isn’t dangerous, but it will be absorbed more quickly. A tip for young kids or thin adults is to inject at a 45 degree angle in order to avoid the muscle.

How Do You Know How Much Insulin to Use?

Knowing what your blood sugar level is before administering insulin is important, particularly around mealtimes, so that the insulin dose can be matched to your blood sugar level and what you are eating. Blood sugar monitoring has evolved over time, from urine glucose testing in the 1950s to the advent of home fingerstick glucometers in the 1980s to now continuous glucose monitoring (CGM) in the 2000s.

In recent years, the professional societies involved in diabetes care, including the American Diabetes Association, have stated that CGM is the standard of care for individuals with type 1 diabetes. In other words: It’s a must for anyone with T1D. These devices monitor the interstitial glucose—glucose that diffuses out of the small blood vessels under the skin, a measure of overall blood glucose—every 1 to 5 minutes and feed that information to patients either on a receiving device or a smartphone. CGMs have revolutionized the care of individuals with type 1 diabetes and been shown to be both extremely safe and efficacious.

One of the other major benefits of CGM is that you can opt to share that data with friends and family, so that alerts for extreme high or low blood sugars can inform treatment decisions and prevent adverse events such as severe hypoglycemia or diabetic ketoacidosis.

Insulin Injection FAQs

Where Should Insulin NOT Be Injected?

It is advisable to avoid scar tissue, stretch marks, and moles. Injecting in these areas will either impede the absorption or lead to erratic absorption of the insulin.

Where Is Injected Insulin Absorbed the Fastest?

The abdomen is the fastest area of the body for insulin absorption.

Should You Pinch the Skin When Using an Insulin Pen?

Yes. “Pinch an inch” is a helpful phrase to remember when giving yourself or another person insulin by pen or syringe.

Where on the Thigh Should You Inject Insulin?

You should inject insulin in the upper outer thigh. Avoid the inner thigh or lower leg so as not to hit any blood vessels or nerves.

Can You Inject Insulin Above the Belly Button?

Yes, insulin can be injected above the belly button so long as it is spaced 2 inches from the belly button. This is because there is connective tissue called fascia under the belly button which is tough and cannot absorb insulin.

What Happens if You Don’t Rotate Injection Sites?

If insulin injection sites are not rotated, then hard knots develop underneath the skin which are unable to absorb insulin. This can lead to a person believing that they are receiving their insulin, but in fact no insulin is being absorbed. This is a very dangerous situation for both patients and providers, who may then increase insulin doses without realizing that the real issue is an absorption problem.